I've been on both sides of the humilation coin and it can be a wonderful cycle of arousal, then embarassment for that arousal, more arousal, feeling vulnerable because of the exposure, and feeling even more arousal. For me, there must also be a sense of trust that the play partner won't push too far.
For me, at least, much of it stems from being found out to be a sexual being by those whom you would generally not be sexual around. Job related humiliation (especially with the threat of being caught) is quite a kicker. Getting my g/f to come while at her office or being made to strip in my own can add a certain 'wow' factor to sex.
I have to agree with moptop about the pics, tho. It seems less humiliation and more debasement when you send pictures of yourself to random strangers, especially when there is no danger of those strangers ever coming in contact with you in r/l. I also find the female form to be beautiful and marvelous--neither we nor our desires are filthy. I found the words painted on her skin made me sad and bothered, not hot and bothered.
However, echoing others, if it gets your motor running and is consensual, then go for it. If it does not, communicate that to your play partner. There are plenty of other things that you can do instead.